Process of electrolytically dissolving iron-oxid scale.



foot. 5

UNITED STA? OFFICE PROCESS OF ELECTROLYTICALLY DlSSOLVlNG IRON-OXIDSCALE.

Specification of Letters Patent.

Patented July 31, 1906.

Application filed June 26, 1905. Serial No. 267,129.

To (all, whom. it II'Mbi/ concern.-

Be it known that I, Crmnurs J. REED, a citizen of the United States,rcsidi'm at Philadelphia, in the county of Philadelphia and State ofPennsylvania, have invented certain new and useful Improvements inProcesses of Electrolytically Dissolving Iron-Oxid Scale, of which thefollowing is a specification.

Various electrolytic methods have been proposed for removing the oxidscale from iron sheets, rods, and wire. In some of these the ironarticle is made the anode in an electrol to of acid or an acid salt. Thescale is t 1115 dissolved more rapidly than in the usual ickle-bath; butthe action is apt to be irregu er, the activity of the acid anionfreuently causing pitting of the iron. Furt ermore, the gain in time ismore than offset by the mat of the electric current. In other proposedmethods the iron article is made the cathode in an electrolyte which isneutral, weakly acid, or alkaline for example, a dilute solution of analkali-metal salt, an acid, or an alt all. The removal of scale,however, is slmv and irregular, spots of scale being fre quently left atvarious points. Some of the scale is also loosened by the electrolytichydro en and drops into the both. In neutral or a lraline solutions muchof the scale is reduced to metallic iron, producing a rough irregularscprfacc. h

Accor in to the es t inv ntion t e iron article is madeth fzag-goflei iiamctrolyteo'f"as'tr'origaqueous tft1on of an acid and the scale iselectrolytically and rapidly dissolved without dissolvin any metalliciron. In the preferred mod c of procedure the electrolyte consists of anaqueous solution of igifullc acid having a specific gravity of about1.20 ezfiiivalent to an acid content of 27.1 or coat, although oodresults may be obtained with solutions having a specific gravity between115 and 1.25". When the acid concentration is below nine per cent, theaction is too slow and irregular to be of much commercial value.

abfi'fiforty'tosefirity ampfes per square While the process is notlimited'to the use of an electrolyte at any particular temperature, theremoval of scale is found to be effected much more re idly, efliciently,and economically at a hi temperature. The electrolyte is preferailymaintained at a temperature of centigrade. Even higher temperatures maybe used; but above 66" The anoden a be of lead and the current densityat the cathode centigrade there is a greater tendency for the acid todissolve the metallic iron, and a higher current density is required toprevent such solution.

Under the s ecified conditions the heavy scale on rolle -iron rods iscompletely re moved in from two to three minutes. The disappearance ofthe scale is not due to the reduction of the oxid to metallic iron. Itis found that the oxid is reduced sim ly to a lower state of oxidationand electro ytically dissolved. When a solution of sulfuric acid isemployed, ox gen is liberated at the anode and ferroussuliate isproduced at the oathodef lhe solution of the oxid, however, is effectedwithout dissolving any of the iron, as in processes in which the articleis. made the anode.

The use of an acid solution thus effects novel and unforeseen results atthe cathode, enabling the scale to be electrolytically removed Withoutdissolving metallic iron in so short a time and at so small a cost forelectric current that the process is commercially available.

I claim- 1. The process of electrolytically dissolving iron-oxid scalefrom the surface of metal, which consists in subjecting the metal as acathode to the action of an electric current while-in contact with anelectrolyte containing sulfuric acid of a specific gravity above 1.06",as set forth.

2. The process of electrolytically dissolving iron-oxid scale from thesurface of metal, which consists in subjecting the metal as a cathode tothe action of an electric current while in contact with an electrolytecontaining sulfuric acid of a specific gravity between 1.15 and 1.25",as set forth.

3. The process of electrolytically dissolving iron-oxid scale from thesurface of metal, which consists in placin' the metal in a stronsolution of an acid, an passing to the meta as a cathode an electriccurrent of suffieient density to rapidly remove the scale, as set forth.

cathode, an electric current of a density not less than forty amperesper square foot, as set forth. 5. The process of electrolyticallydissolvin, iron-oxid scale from the surface of metal, 1 Which'consistsin placing the metal in a solution of sulfuric acid having, a specificgravity between 1.15 and 1.25, and passing to the metal as a cathode, anelectric current of a density not less than forty amperes per squarefoot, as set forth.

6. The process of electrolytically dissolving iron-oxid scale from thesurface of metal, which consists in placing the metal in astrongsolution of an acid, and passing to the metal as a cathode, from ananode of lead, an eleotrio current of sufficient density to rapidlylremove the scale, as set forth.

7. The process of electrolytically dissolving iron-oxid scale from thesurface of metal, which consists in placing the metal in a solution ofsulfuric acid having a specific gravity of about 120, and passing to themetal as a cathode, from an anode of lead, an electric current ofsufficient density to rapidly remove the scale, as set forth.

In testimony whereof I aflix my signature in presence of two Witnesses.

CHARLES J. REED. Witnesses:

J. W. RITTER, W. A. RoBBINs.

